Overall, 133.7 million people shopped in stores and online over the four-day weekend, down 5.2 percent from last year, according to a survey of 4,631 people conducted by Prosper Insights & Analytics for the trade group.

Total spending for the weekend is expected to fall 11 percent to $50.9 billion from an estimated $57.4 billion last year, the trade group estimated.

Part of the reason is that Target, J.C. Penney, Macy's, Wal-Mart and other major retailers pushed fat discounts as early as Halloween. Some opened stores even earlier on Thanksgiving. All that stole some thunder from Black Friday and the rest of the weekend.

Still, the preliminary data makes retailers worried that shoppers remain frugal despite improving employment and falling gas prices.

A St. Louis County grand jury has brought no criminal charges against Darren Wilson, a white police officer who fatally shot Michael Brown, an unarmed African-American teenager, more than three months ago in nearby Ferguson.

At a news conference, the St. Louis County prosecutor, Robert P. McCulloch, said that members of the grand jury deliberated for more than two days before finding that no probable cause existed to file charges against Officer Wilson.

The decision set off a new wave of anger among hundreds who gathered outside the Ferguson Police Department. Police in riot gear stood in a line as demonstrators chanted and threw signs and other objects toward them as the news spread. One woman said: “The system failed us again.”

Mr. Brown’s family issued a statement expressing sadness but calling for peaceful protest and a campaign for body cameras on police officers nationwide. “We are profoundly disappointed that the killer of our child will not face the consequence of his actions,” the statement said. “While we understand that many others share our pain, we ask that you channel your frustration in ways that will make a positive change. We need to work together to fix the system that allowed this to happen.”